Laughing out loud: scientists have made new discoveries about laughter

The Science of Laughs

Scanning brains and eavesdropping on chimps, researchers are figuring out why we chuckle, guffaw and crack up. Hint: it isn’t funny.

By Sharon Begley

NEWSWEEK

      October 9 issue: The man was known around town as a

chronic borrower, always asking the neighbors to lend him one

tool or another. So when he strolled over to Mr. Green one

Sunday and asked, “Say, are you using your lawn mower today?”

Green had a ready answer. “Yes, I am,” he said emphatically.

         TO WHICH THE would-be borrower replied, "Great! Then

since you won't need your golf clubs, I'll just borrow those."

        If you are like most people, that punch line triggered

at least one short exhalation of breath chopped into staccato

segments lasting about one fifteenth of a second each and spaced

one fifth of a second apart. In other words, laughter. Exactly

why humor causes this acoustic response (rather than, say, sweaty

palms or any other physiological reaction) has been lost in the

mists of evolution. Thinkers from Plato and Aristotle to Kant,

Darwin and Freud have tried to fathom laughter (Plato feared it

would disrupt the state, and Kant theorized that it arises when

what you expect to happen doesn't, which is why surprising punch

lines work), but they've been long on philosophy and short on

science. Lately, though, an intrepid band of researchers has

been trying to remedy that. With techniques like MRI brain scans

to probe why people cannot tickle themselves into paroxysms of

laughter, they are tackling "one of the last great unsolved

problems in human behavior," says neuroscientist Robert Provine

of the University of Maryland, whose book, "Laughter: A

Scientific Investigation," will be published next week. And no,

he's not referring to why guys are always walking into bars with

ducks under their arms.

 "Laughter," says Provine, "is a probe into such fundamental

questions as why humans can speak but other apes can't."

ROBERT PROVINE

University of Maryland

           To investigate the roots of laughter, scientists have

turned to our primate cousins. If you tickle a chimp (carefully;

and preferably a baby), it will likely laugh, but the sound

doesn_t resemble human laughter so much as it does panting, with

one sound per inhale and exhale. Provine realized that the

reason chimps cannot emit a string of "ho ho ho's" is that they

cannot make more than a single sound when they exhale or inhale.

Humans, in contrast, can chop up a single exhalation into

multiple bursts of "ha ha ha" or words. (Speech results from

chopping up an exhalation into separate sounds.) "Laughter,"

says Provine, "is a probe into such fundamental questions as why

humans can speak but other apes can't." No humanlike laughing,

no speaking.

        The fact that chimps pant while playing suggests that

laughter evolved from the heavy breathing that accompanies

something like playful wrestling. Ritualized

panting laughter then might have come to represent the playful

activity itself, signaling "I'm enjoying this." For there is no

question that human laughter is a social behavior. (You would

have laughed more at the borrow-the-mower joke if you had heard

it read aloud while in a group, rather than reading it silently

and alone.)

        But what do titters communicate? Some clues come from

Provine's collection of 1,200 "laugh episodes," from

eavesdropping in public places. He finds that speakers laugh

more than listeners, and women laugh at men more than vice

versa. (Laughing behind their backs doesn't count.) Laughter

seems to signal an attempt to ingratiate oneself: in India,

notes Provine, men of lower castes giggle when addressing men of

higher castes, but never the other way round. People in power

seldom giggle. More evidence that laughing has less to do with

humor than with social signals is that, in Provine's 1,200

samples, by far the remarks that most often elicited laughter

were of the _it was nice meeting you, too" or "I know" variety.

In other words, witless. "Laughter is only rarely a response to

jokes," says Provine. "It is, instead, the quintessential human

social signal. It solidifies relationships and pulls people into

the fold." And not only for the good. The Columbine killers

laughed as they shot, demonstrating solidarity with each other

and, needless to say, not their targets. Evil laughter is no

oxymoron.

        Laughter is contagious, for reasons that remain pretty

murky, but while you can catch it from others you can_t induce

it in yourself. Forced laughter sounds, well, forced. And

tickling yourself is a non-starter. There have been all sorts of

theories about why, but recent experiments led by Sarah-Jayne

Blakemore of University College, London, may have finally

revealed the answer. The neuroscientists used functional MRI to

(noninvasively) peer into the brains of volunteers who either

tickled themselves or were tickled by a robotic tickler.

The fMRI detected more neuronal activity in the somatosensory

cortex, the part of the brain that registers touch, when people

were tickled than when they tickled themselves. The reason seems

to be that when you move your fingers to, say, tickle your rib

cage, the cerebellum, which coordinates complex movements,

predicts what that will feel like and sends out a signal to

cancel the sensory response much as the military can jam an

enemy radio transmission if it knows the frequency ahead of

time. But if the tickle comes from someone else, and so is a

surprise, the cerebellum can't block it. Self-tickling thus

seems to make neurons fire in a way that blocks activation of

the part of the brain that ordinarily processes touch.

        Laughter seems intimately entwined with our physiology.

It blocks a neural reflex that regulates muscle tone, proving

that _going weak with laughter_ is more than a metaphor. Tumors

or lesions of the brain's hypothalamus, which regulates basic

processes like respiration, can cause bouts of uncontrolled

laughter. And although laughter seems to have evolved because of

the message it sends to others, it may have a therapeutic effect

on the laugher, too: it can raise heart rate as much as aerobic

exercise, lessen the perception of pain and increase tolerance

of discomfort. While the scientists work out how a good chuckle

does all this, have you heard the one about the priest, the

minister and the rabbi... ?

       ) 2000 Newsweek, Inc.